Write TypeScript guide

[shaydewael]

Description

While the Using TypeScript page exists, it's very unhelpful and doesn't explain how Bolt's type system works, or how to refine/customize types.

What type of issue is this? (place an x in one of the [ ])

• [ ] bug
• [ ] enhancement (feature request)
• [ ] question
• [x] documentation related
• [ ] example code related
• [ ] testing related
• [ ] discussion

Requirements (place an x in each of the [ ])

• [x] I've read and understood the Contributing guidelines and have done my best effort to follow them.
• [x] I've read and agree to the Code of Conduct.
• [x] I've searched for any related issues and avoided creating a duplicate issue.

[filmaj]

Setting this to the 5.0.0 milestone which is when we plan to revamp the type system in bolt.

[david-alpert-os]

The Using Typescript link posted above now gives a 404